Update load image timeout based on benchmarking.

Author: fenxiong

agent/dockerclient/timeout.go

@@ -23,10 +23,14 @@ const (
 	ListImagesTimeout = 10 * time.Minute
 	// LoadImageTimeout is the timeout for the LoadImage API. It's set
 	// to much lower value than pullImageTimeout as it involves loading
-	// image from either a file or STDIN
-	// calls involved.
-	// TODO: Benchmark and re-evaluate this value
-	LoadImageTimeout = 10 * time.Minute
+	// image from either a file or STDIN calls involved.
+	// This value is set based on benchmarking the time of loading the pause container image,
+	// since it's currently only used to load that image. If this is to be used to load any
+	// other image in the future, additional benchmarking will be required.
+	// Per benchmark, 2 min is roughly 4x of the worst case (29s) across 400 image loads on
+	// al1/al2/al2gpu/al2arm with smallest instance type available (t2.nano/a1.medium) and
+	// burst balance = 0.
+	LoadImageTimeout = 2 * time.Minute
 	// RemoveImageTimeout is the timeout for the RemoveImage API.
 	RemoveImageTimeout = 3 * time.Minute